Independent developer guide
Jev by TypeSafe.
Decisions, not chat.
The independent launch guide to Jev — what the System One model is, how to access it, and what to build first.
Typed answers
Parallel decisions
Fixed output space
system_one.evaluatetyped
State: “A customer reports a duplicate charge and asks for help.”
billing0.94
technical0.04
other0.02
Your code defines the choices. Jev returns probabilities your application can act on.
Verified resource map
Go from curious to running code.
Official sources come first. Community examples are labeled as community resources, and vendor performance claims stay attributed to their source.
Official & Getting Started
Primary sources from TypeSafe: the launch announcement, documentation, quickstart, and console.
TypeSafe AI
The company building Jev and the System One model family.
Official
TypeSafe
Jev
TypeSafe Documentation
Official concepts, API guides, primitives, and reference material for Jev.
Official
Documentation
API
Jev Quickstart
The official path from API key to a first System One request.
Official
Quickstart
Code
TypeSafe Console
Sign in, request access, and work with Jev through TypeSafe's console.
Official
Console
Access
Introducing System One Models & Jev
TypeSafe's September 2026 launch post with the model's design, claims, benchmarks, and caveats.
Official
Launch
Evidence
TypeSafe Manifesto
The company's case for AI interfaces designed for software rather than conversation.
Official
Vision
System One
API Access
Verified ways to call Jev directly or through OpenRouter and Vercel AI Gateway.
TypeSafe Direct API
Use the native System One API and official Jev model identifiers through TypeSafe.
Direct API
Official
Early Access
OpenRouter — TypeSafe
Browse Jev models, current pricing, context limits, and provider availability on OpenRouter.
OpenRouter
Provider
Pricing
OpenRouter — Jev Latest
The rolling OpenRouter alias that points to the latest model in the Jev family.
OpenRouter
Jev Latest
API
Vercel AI Gateway — Jev
Call Jev through Vercel's evaluation API, native HTTP endpoint, or a TypeSafe client.
Vercel
AI Gateway
TypeScript
SDKs & Integrations
Official client libraries, adapters, and integrations for adding Jev to an application.
TypeSafe JavaScript SDK
The official TypeScript and JavaScript client for the TypeSafe API.
Official
JavaScript
TypeScript
TypeSafe Python SDK
The official Python client for Jev and the TypeSafe API.
Official
Python
SDK
TypeSafe Agent Skills
Official agent skills for building against the System One API.
Official
Agents
Skills
System One Adapter for Python
TypeSafe's adapter for using LLM APIs behind a System One-compatible client.
Official
Python
Adapter
Pydantic AI — TypeSafe
Pydantic AI documentation for TypeSafe models and typed evaluation workflows.
Pydantic
Python
Integration
Concepts
Understand System One and the typed question primitives behind Jev decisions.
System One
The official overview of models that turn shared state into typed probabilistic decisions.
Official
Concept
System One
Question Primitives
The official starting point for the Choice, Score, and Noul question types.
Official
Primitives
Questions
Choice
Select one value from an answer space your application defines in advance.
Official
Classification
Routing
Score
Evaluate state against an ordered rubric and receive a typed probabilistic score.
Official
Scoring
Rubric
Noul
Ask a bounded yes-or-no question and use the returned probability in application logic.
Official
Boolean
Guardrail
Examples & Evaluations
Worked examples, evaluation workflows, and code showing how Jev fits into software.
TypeSafe Workflow Evaluations
Official evaluation workflows and supporting evidence behind TypeSafe's published comparisons.
Official
Evaluations
Benchmarks
TypeSafe Router
A TypeSafe project showing model and tool routing with Jev's native decision format.
Routing
Example
GitHub
Jev with Vercel AI SDK
Vercel's explanation and code examples for Choice, Score, and Boolean evaluations.
Vercel
AI SDK
Tutorial
Vercel TypeSafe API Guide
Use an existing TypeSafe client, HTTP API, or AI SDK through Vercel AI Gateway.
Vercel
HTTP API
Example
Community Guides
Clearly labeled third-party tutorials and community-curated Jev project collections.
LangChain — Building a Harness with Jev
A third-party technical walkthrough of using Jev inside a constrained software workflow.
Community
LangChain
Harness
Awesome Jev Use Cases
A community-maintained list of demos and repositories; useful for discovery, not an official project count.
Community
Use Cases
Directory
TypeSafe Jev Examples
Community examples for calling Jev through OpenRouter and applying confidence-gated decisions.
Community
OpenRouter
Examples
Flavio Copes — Jev
A concise third-party introduction with JavaScript, Python, and curl examples.
Community
Tutorial
Code
Jev guides
More guides →What Is Jev? TypeSafe's System One Model
→A practical explanation of Jev, how System One differs from a language model, and when typed probabilistic decisions are useful.
Jev Playground: How to Test Your First Decision
→A practical walkthrough for testing Jev in the TypeSafe console, designing a useful first question, and evaluating the result before writing production code.
What Is Noul in Jev? A Practical Guide
→Learn how Jev's Noul primitive returns a yes probability, when to use it instead of Choice or Score, and how to turn uncertainty into safe code.
Jev API Access: TypeSafe, OpenRouter, and Vercel
→Compare the verified ways to access Jev, including the native TypeSafe API, OpenRouter, and Vercel AI Gateway.
Jev Alternatives: Rules, Classifiers, and LLMs
→Compare Jev with deterministic rules, trained classifiers, GLiNER, and general language models for routing, scoring, extraction, and typed decisions.
Jev Pricing: What the Published Numbers Mean
→Understand Jev's published input pricing, free output, provider differences, and the costs a token price does not capture.